1. Field Of The Invention
The present invention relates generally to a tape measure-type apparatus, and more particularly to a distance-measuring tape measure-type apparatus having the same set of scales on both sides of the tape for two separate, different and distinct uses. Even more particularly, the present invention relates to an airman's or pilot's distance-measuring tape having a set of graduated scales on both sides of the tape for measuring distances in one or more of nautical miles, statute miles, and kilometers, and having one side calibrated for a first conventional aeronautical chart and the opposite side calibrated for a second different and distinct aeronautical chart.
2. Description Of The Prior Art
Many types of navigational instruments have been used in the prior art for measuring distances and/or course headings between a point of departure or a first point and a point of destination or a second point on aeronautical navigational charts. Instruments such as protractors, compasses, dividers, and rulers having distance scales thereon have been tried. Most are too complicated, cumbersome, and limited in use, and they require too much time and to many motions to plot and measure a course. A pilot generally needs a quick and easy way to measure distance accurately on an aeronautical chart.
Furthermore, most pilots and navigators today use a relatively short ruler having a straight edge calibrated in only one of nautical mile, statute miles or kilometers and useful with only one type of aeronautical chart having miles or kilometers. These short rulers are inaccurate, prone to error, difficult to use when long distances are involved, and limited in use with any other type of aeronautical chart or with different types of distance-measuring scales.
In time, the industry has migrated toward to the use of such relatively short rulers which have many different and often confusing scales provided on them. In measuring long distances on an aeronautical chart, the short rulers are cumbersome and relatively inaccurate. If the scales on the charts themselves are used, then some other device must be used as a yard stick, compass, dividers, string or the like, which again is very clumsy, difficult to use, and inaccurate.
For example, U.S. Pat. No. 3,651,574 illustrates an extremely awkward, cumbersome, difficult-to-use apparatus for measuring distance and plotting a course heading. In this invention, one end of the device must be physically aligned with an edge of the chart, a slide must be extended, and a ruler mounted on a compass rose must be rotated so that a tape strip can be stretched from point of destination to point of departure. The graduated scale on this particular tape role is only disposed on one side of the tape strip, and it's designed so that it could not be used or pulled out with its opposite side face up. It is calibrated in only one set of units such as statute miles, kilometers, or nautical miles. While the tape can be moved, by rotating it ninety degrees, this is only to move it from a "use" position to a "storage" position, and not to access the opposite side of the tape. This instrument is limited to use in one distance scale on either of two types of aeronautical charts which means you would need a second totally separate instrument if you wanted to measure in different distance units.
The present invention solves substantially all of the problems of the prior art by providing a simple, compact, light-weight, non-cumbersome, easy-to-use, easy-to-read, easy-to-store measuring device which can be used to quickly and easily measure distances on two different and distinct types of aeronautical charts and in a plurality of distance-measuring units such as nautical miles, statute miles, and/or kilometers.